Disease-related anaerobic gliding bacteria (Capnocytophaga) were isolated from the human oral cavity. Electron microscopic examination of thin-sections of chemically fixed cells revealed them to contain a periplasmic space of variable dimension and electron density. Electron microscopic and chemical localization and characterization of the hydrolytic enzyme alkaline phosphatase (APase) revealed it to be situated in the periplasm. The more virulent Capnocytophaga sputigena possessed twice as much APase activity than C. ochraceus and C. gingivalis. Localization of collagenase, elastase and other nucleotidases is in progress. High levels of branched chain fatty acids have been found in the capnobacteria; their significance and contribution to host tissue destruction is being evaluated; similar undertakings regarding secondary and tertiary amines has revealed large amounts of these compounds in several members of the genus Bacteroides. Studies involving the effects of these compounds on tissue culture cells is being planned. An extensive ultrastructural study on the surface structure of representative Capnocytophaga, Bacteroides and Eikenella has revealed large amounts of surface exopolymers of in vitro grown cells. These polymers not only join adjacent cells into a tight aggregate, but appear to attach the cells to the support surface. The contribution of these exopolymers to an in vivo existance is under examination.